I have not used sliders, have looked at them but haven't used them. With that said, looking at a slider from a mechanical standpoint I just cannot agree with the part I highlighted above. IMO a slider DOES let the rear eye of the spring to move forward and aft. I don't understand how you can say it doesn't. When the arch becomes greater on a leaf spring (shortens up) the slider allows the rear spring eye/bushing/assy to slide forward (hence the name "slider"). When the spring flattens out the eye slides rearward. I'm not promoting sliders. Just pointing out that mechanically I believe you are looking at it wrong
I would like to add that I have not measured how much a slider will actually let a spring move for and aft so it's possible a shackle will let it move more, nevertheless a slider does not bind the spring solid forcing the spring to "distort, as you say" such as bolting it solidly to the frame would. If a slider worked that way what would be any purpose of having it? Just bolt the spring to the frame [-X
